The present invention relates to a cordless key telephone system. It Is known that multiple tenants are served by a single, wired key telephone system by dividing exchange lines as well as key telephone stations into groups according to the tenants and wiring so that connections are established exclusively between the exchange lines and telephone sets of the same group by a common, connection setup unit. This is achieved by storing tenant data into a memory at the central site and checking a line indication supplied from a station set with the stored tenant data to determine whether it is authorized to access the indicated exchange line.
Cordless key telephone systems have been in widespread use to take advantage of their complete elimination of the wiring network and flexible location of cordless stations. However, cordless key telephone systems with multiple tenant facility have not yet been developed, and a need has been felt for implementing such systems.
One logical extension of the wired key telephone system with multiple tenant facility to a cordless key telephone system would be to install a memory at the central site of the system. However, each cordless station would be required to transmit a line indication during a call setup to allow the central site to determine whether the calling party is authorized to access the line indicated. If exchange lines are frequently seized by unauthorized cordless stations when originating a call, channel resources of the system would be wasted because the central site cannot provide tenant check until connections are set up. In addition, the time taken for the central site to transmit a ringing signal in response to an incoming call would become prohibitively long because of the necessity to check all cordless stations against tenant data.